19 Variance/SD  PopulationThe average squared distance/deviation of all raw scores from the meanThe standard deviation squaredStatistical notation: σ2Scale of measurement:Interval or ratioAdvantages:Considers all dataNot a terminal statisticDisadvantages:Not appropriate for nominal or ordinal dataSensitive to extreme outliers

20 Variance/SD  PopulationStandard deviation:The average distance/deviation of all raw scores from the meanThe square root of the varianceStatistical notation: σScale of measurement:Interval or ratioAdvantages and disadvantages:Similar to variance

21 Calculation of the Variance  PopulationWhy square all values?If all deviations from the mean are summed, the answer always = 0